The Reaching for Excellence in Adolescent Care and Health (REACH) Project is a ulticenter longitudinal study funded by the National Institute of Child Health and Human Development (NICHD), the National Institute of Allergy and Infectious Disease (NIAID), the National Institute on Drug Abuse (NIDA), and the Health Resources and Services Administration (HRSA) to research the medical, biobehavioral, and psychological aspects of HIV/AIDS, including access to care and its use, in adolescents infected with HIV through sexual or drug-taking behaviors. Approximately 240 HIV- positive and 120 HIV-negative subjects, ages 12 through 18 years, will be recruited into this protocol which will measure health status, service utilization, sexual and and drug-taking behaviors, sexually transmitted disease and viral coinfection, and psychological state. Subjects will be seen at three month intervals over the duration of the project. The ultimate goal of this project is to achieve a better understanding of HIV disease progression and co-morbidity in adolescents and thus improve health care management. This goal will be addressed through the initial enrollment of approximately 200 HIV-infected adolescents into a standardized base protocol to characterize population-based spectrum of disease, disease progression, and the effect of co-morbidity with other sexually-transmitted disease and pregnancy in the adolescent population; and the tandardization and evaluation of health care services. The objectives of this project are to examine the pathogenesis of HIV infection, including spectrum of disease, in treated and untreated adolescents ages 12-18 and to ompare the pathogenesis of HIV infection in adolescents to that described for adults and children. To examine the effects of HIV infection on normal physiologic growth and development in HIV-infected adolescents, the morbidity associated with co-infection with sexually transmitted disease that commonly occur in adolescents and to compare these morbidities between HIV-positive and HIV-negative adolescents, the role of mental health on disease progression, and potential immunologic and immunogenetic markers or disease progression specific to adolescents infected with HIV.